FWIW Nvidia is developing their own Shield TV remote app (for iOS and Android phones), which will hopefully be more reliable than Google's bare-bone Android TV Remote Control app (also on iOS and Google Play store).
It'll even have a virtual mouse pad.
Cetusplay
I’m not going to link it, because that’s just obnoxious....lol, however Peel has been around the longest of them all. I reckon there’s a reason 😬
https://play.google.com/store/apps/details?id=fr.bouyguestelecom.remote
This is a two part app. Part one linked above is installed on your phone/tablet. Part two is installed on your Android TV device. This method adds CEC volume control, device rest mode, direct app controls. This app on an old tablet has become my go-to control on my Nvidia shield.